Hello,
I am very very very new to Unix, but experienced in C. I wasn't sure whether this Message fits the Unix forum (if there's one), or C. But, since it is a compiling Error, I felt it fits here best.

I did a "make", compilation, to a program called ioquake3. I get these errors. I tried to google them. It seems that these errors are caused by double inclusions, or something of the sort.
I tried endlessly to see how to make the write edits to the code. But, I couldn't fix it.

make[2]: `build/release-linux-x86_64/ioq3ded.x86_64' is up to date.
CC code/client/cl_cgame.c
In file included from code/client/cl_cgame.c:24:
code/client/client.h:40: error: expected '=', ',', ';', 'asm' or '__attribute__' before '*' token
code/client/client.h:41: error: expected declaration specifiers or '...' before '*' token
code/client/client.h:41: error: expected ')' before '*' token
code/client/client.h:42: error: expected declaration specifiers or '...' before '*' token
code/client/client.h:42: error: expected ')' before '*' token
code/client/client.h:43: error: expected ')' before '*' token
code/client/client.h:44: error: expected declaration specifiers or '...' before '*' token
code/client/client.h:44: error: expected ')' before '*' token
code/client/client.h:45: error: expected ')' before '*' token
code/client/client.h:46: warning: parameter names (without types) in function declaration
code/client/client.h:48: error: expected '=', ',', ';', 'asm' or '__attribute__' before '*' token
code/client/client.h:49: error: expected declaration specifiers or '...' before '*' token
code/client/client.h:49: error: expected ')' before '*' token
code/client/client.h:51: error: expected declaration specifiers or '...' before '*' token
code/client/client.h:51: error: expected ')' before '*' token
code/client/client.h:53: error: expected declaration specifiers or '...' before '*' token
code/client/client.h:53: error: expected ')' before '*' token
code/client/client.h:58: error: expected declaration specifiers or '...' before '*' token
code/client/client.h:58: error: expected ')' before '*' token
code/client/client.h:60: error: expected declaration specifiers or '...' before '*' token
code/client/client.h:60: error: expected ')' before '*' token
code/client/client.h:61: error: expected '=', ',', ';', 'asm' or '__attribute__' before '*' token
code/client/client.h:63: warning: parameter names (without types) in function declaration
In file included from code/client/cl_cgame.c:24:
code/client/client.h:264: error: expected specifier-qualifier-list before 'CURL'
code/client/cl_cgame.c: In function 'CL_GetServerCommand':
code/client/cl_cgame.c:276: error: 'clientConnection_t' has no member named 'demoplaying'
code/client/cl_cgame.c: In function 'CL_InitCGame':
code/client/cl_cgame.c:751: error: 'clientConnection_t' has no member named 'demoplaying'
code/client/cl_cgame.c: In function 'CL_CGameRendering':
code/client/cl_cgame.c:799: error: 'clientConnection_t' has no member named 'demoplaying'
code/client/cl_cgame.c: In function 'CL_AdjustTimeDelta':
code/client/cl_cgame.c:834: error: 'clientConnection_t' has no member named 'demoplaying'
code/client/cl_cgame.c: In function 'CL_FirstSnapshot':
code/client/cl_cgame.c:900: error: 'clientConnection_t' has no member named 'timeDemoBaseTime'
code/client/cl_cgame.c:919: error: 'clientConnection_t' has no member named 'speexInitialized'
code/client/cl_cgame.c:921: error: 'clientConnection_t' has no member named 'speexEncoderBits'
code/client/cl_cgame.c:922: error: 'clientConnection_t' has no member named 'speexEncoderBits'
code/client/cl_cgame.c:924: error: 'clientConnection_t' has no member named 'speexEncoder'
code/client/cl_cgame.c:926: error: 'clientConnection_t' has no member named 'speexEncoder'
code/client/cl_cgame.c:927: error: 'clientConnection_t' has no member named 'speexFrameSize'
code/client/cl_cgame.c:928: error: 'clientConnection_t' has no member named 'speexEncoder'
code/client/cl_cgame.c:929: error: 'clientConnection_t' has no member named 'speexSampleRate'
code/client/cl_cgame.c:931: error: 'clientConnection_t' has no member named 'speexPreprocessor'
code/client/cl_cgame.c:931: error: 'clientConnection_t' has no member named 'speexFrameSize'
code/client/cl_cgame.c:932: error: 'clientConnection_t' has no member named 'speexSampleRate'
code/client/cl_cgame.c:935: error: 'clientConnection_t' has no member named 'speexPreprocessor'
code/client/cl_cgame.c:939: error: 'clientConnection_t' has no member named 'speexPreprocessor'
code/client/cl_cgame.c:943: error: 'clientConnection_t' has no member named 'speexDecoderBits'
code/client/cl_cgame.c:944: error: 'clientConnection_t' has no member named 'speexDecoderBits'
code/client/cl_cgame.c:945: error: 'clientConnection_t' has no member named 'speexDecoder'
code/client/cl_cgame.c:946: error: 'clientConnection_t' has no member named 'voipIgnore'
code/client/cl_cgame.c:947: error: 'clientConnection_t' has no member named 'voipGain'
code/client/cl_cgame.c:949: error: 'clientConnection_t' has no member named 'speexInitialized'
code/client/cl_cgame.c:950: error: 'clientConnection_t' has no member named 'voipMuteAll'
code/client/cl_cgame.c:953: error: 'clientConnection_t' has no member named 'voipTarget1'
code/client/cl_cgame.c:953: error: 'clientConnection_t' has no member named 'voipTarget2'
code/client/cl_cgame.c:953: error: 'clientConnection_t' has no member named 'voipTarget3'
code/client/cl_cgame.c: In function 'CL_SetCGameTime':
code/client/cl_cgame.c:969: error: 'clientConnection_t' has no member named 'demoplaying'
code/client/cl_cgame.c:972: error: 'clientConnection_t' has no member named 'firstDemoFrameSkipped'
code/client/cl_cgame.c:973: error: 'clientConnection_t' has no member named 'firstDemoFrameSkipped'
code/client/cl_cgame.c:1006: error: 'clientConnection_t' has no member named 'demoplaying'
code/client/cl_cgame.c:1045: error: 'clientConnection_t' has no member named 'demoplaying'
code/client/cl_cgame.c:1061: error: 'clientConnection_t' has no member named 'timeDemoStart'
code/client/cl_cgame.c:1062: error: 'clientConnection_t' has no member named 'timeDemoStart'
code/client/cl_cgame.c:1062: error: 'clientConnection_t' has no member named 'timeDemoLastFrame'
code/client/cl_cgame.c:1063: error: 'clientConnection_t' has no member named 'timeDemoMinDuration'
code/client/cl_cgame.c:1064: error: 'clientConnection_t' has no member named 'timeDemoMaxDuration'
code/client/cl_cgame.c:1067: error: 'clientConnection_t' has no member named 'timeDemoLastFrame'
code/client/cl_cgame.c:1068: error: 'clientConnection_t' has no member named 'timeDemoLastFrame'
code/client/cl_cgame.c:1071: error: 'clientConnection_t' has no member named 'timeDemoFrames'
code/client/cl_cgame.c:1073: error: 'clientConnection_t' has no member named 'timeDemoMaxDuration'
code/client/cl_cgame.c:1074: error: 'clientConnection_t' has no member named 'timeDemoMaxDuration'
code/client/cl_cgame.c:1076: error: 'clientConnection_t' has no member named 'timeDemoMinDuration'
code/client/cl_cgame.c:1077: error: 'clientConnection_t' has no member named 'timeDemoMinDuration'
code/client/cl_cgame.c:1083: error: 'clientConnection_t' has no member named 'timeDemoDurations'
code/client/cl_cgame.c:1083: error: 'clientConnection_t' has no member named 'timeDemoFrames'
code/client/cl_cgame.c:1087: error: 'clientConnection_t' has no member named 'timeDemoFrames'
code/client/cl_cgame.c:1088: error: 'clientConnection_t' has no member named 'timeDemoBaseTime'
code/client/cl_cgame.c:1088: error: 'clientConnection_t' has no member named 'timeDemoFrames'
make[2]: *** [build/release-linux-x86_64/client/cl_cgame.o] Error 1
make[2]: Leaving directory `/r/home7/yasir/minoru/cfe2/yasirTemp/ioquake3dev/best_linux_20111012/ioquake3dev_clean'
make[1]: *** [targets] Error 2
make[1]: Leaving directory `/r/home7/yasir/minoru/cfe2/yasirTemp/ioquake3dev/best_linux_20111012/ioquake3dev_clean'
make: *** [release] Error 2

The file you have included in your question is client/cl_curl.h which isn't mentioned anywhere in the error log. I don't see anything at or near line 40 of the actual client/client.h that could cause the error, so perhaps you have managed to mangle the file beyond repair. Download a clean copy of the source from http://ioquake3.org/get-it/source-codes/ and try again.

I commented out both, because it was already included in another file that includes this one. (sorry don't remember the names.)
Furthermore, I also wanted to test if the errors would change with the comment or not. I simply forgot to un-comment it when I copy/pasted it back in here.